The computer is finally working and it is time to take a look at our garden soil and decide what it needs for next year to keep producing a bounty of healthy food for us.
Fall is my preferred time to add soil amendments, it means that you have several months for the bacteria and microbes to work on and integrate into the amendments. The worms and other beneficial life forms can colonize the "new soil" and by the time planting season comes around again your amendments should be fully integrated into the soil.
So what is a soil amendment? The most basic definition of a soil amendment is any material which is added to soil to alter the structure and pH of the existing conditions. When you ask gardeners why they amend their soil and they will most often talk about altering the way water moves through their soil and increasing the nutrient availability of soil.
Before you can look at amendments you need to know the mineral composition of your soil and the pH value of your soil. You can see the posts on how to check the mineral composition of your soil here and here. Soil pH testing kits are available at most stores that sell gardening supplies or you can order online.
We get a lot of questions about adding compost and organic matter, most of these regard timing. There is never a bad time to add compost to your soil, but it is easiest to do so in the spring and fall. Generally because there are not a lot of plants in your way and you can work it into the soil. Space is another consideration. If you have a large area for your compost pile(s), then you can start a fresh pile of compost from all the material you take out of the garden in the fall. If your space is limited, you may have to spread your finished compost before you can start a new pile.
When discussing adding organic matter it gets a little trickier. If you want to add organic matter straight to your garden, the most important thing you need to remember is this: as organic matter decomposes it ties up nitrogen. The more fibrous the organic matter is the more nitrogen it ties up and the longer it takes to decompose. This is not a big deal if you are adding leaves to your garden in the fall. In most cases they will completely decompose before spring. If you chose to chop and drop your garden remnants, tougher, more fibrous material such as corn stalks may not decompose before spring. Never add un-composted organic matter during the growing season, it will tie up your available nitrogen and your plants will suffer.
Full disclosure here, we do not have a "compost pile". Everything from food scraps of all kinds, wasted hay yard waste and garden trimmings goes through the pigs. Yep, if they don't eat it the trample it in their bedding and it ends up in the manure pile. Our compost comes from the manure piles.
If your testing shows you have heavy clay soil, your priorities are going to be adding nutrient rich organic matter to increase the fertility. Something to increase drainage and a way to bulk up the soil thereby increasing aeration.
The best candidates for clay soil amendments are compost, and lots of organic material. Most people will tell you if you have clay soil you need to add sand, My short answer is don't. To alter the drainage of a clay soil with sand, you would have to add half, 50% of the current volume of soil to make an effective soil. This quickly gets expensive. Adding less will give you a soil where the larger pore spaces of the sand are filled in by the smaller clay particles, resulting in a denser, heavier more easily compacted soil that still won't drain!
The best thing you can do for your heavy clay soil is to add organic matter that will open the structure of the soil improving drainage and increasing the amount of life in your soil. Wood chips or shavings are very effective. Get in the habit of using these as mulch, and using either on the paths in your garden is a great way to incorporate them into the soil.
Clay soils respond well to green manure, but remember the nitrogen issues. Heavy clay is also an excellent candidate for bio char applications. Ground bark is also an effective amendment for this soil.
Sandy soils are as difficult to deal with as clay. When looking at amendments for sandy soil your objectives are increasing nutrient, slowing down the flow of water through the soil and adding organic matter to increase the amount of soil micro organisms and bacteria.
Compost is still the best way to add available nutrients to the soil. It packs a powerful punch of nutrient that is available to your plants from day 1. Peat moss is my preferred additive for quickly increasing the absorption rate of sandy soils. It is quite acidic so you need to monitor your pH levels carefully . For the long term, adding organic matter is the best way to increased the absorption rate of sandy soils. By adding organic matter, you increase the amount of microorganisms and bacteria which feed on the decaying matter. The excretions and ultimately the decomposing bodies of these organisms combine to form humus, and humus is the 'glue' that holds soil together. So ground bark, and wood chips are again excellent forms of organic matter to add to sandy soils.
A note about ph. Generally, most vegetables prefer a pH that is slightly acidic to neutral. In the range of 5.5 to 7. A comprehensive list can be found here. If you soil is too acidic, the best amendment to sweeten the soil is still ground lime. It is available almost everywhere that sells nursery supplies. It is relatively inexpensive and usually contains clear directions for application rates. If your soil tests out in the alkaline range you will need to add a compound to sour it a little. Gypsum or ground sulfur are the usual candidates. It has been my experience that the availability of these vary from region to region, but one or the other is usually available locally. Again follow directions for application rates.
Hopefully I haven't given you information overload with this topic. Soil building is not going to happen over a single season. It takes time and patience, not my strongest trait. At first it will seem that everything you are doing hasn't made any difference and then one day, you will be out digging in the garden and it will strike you that you have the beautiful, rich black soil you have longed for. so the sooner you start, the sooner you will get there; test your soil composition, know where you need to make changes and get started. This is where your food is coming from..... you need to make it the healthiest it can be!
Have a great day everyone.